mathz of F.2

1)In a basketball playground,the region that is 4m or more from the basket is called the 3-point region.Ben is a good shooter and if his distance from the basket in the 3-point region is d m,his rate of score(G) can be calculated by using the following formula:
G=[320/(d-2)^2]%
(a)Find the scoring rate of Ben in position A.
(b)Find the scoring rate of Ben at the centre of the playground.